From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.2 required=3.0 tests=FROM_EXCESS_BASE64, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 498F7C48BD5 for ; Tue, 25 Jun 2019 18:30:29 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 180092086D for ; Tue, 25 Jun 2019 18:30:29 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 180092086D Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:34594 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.86_2) (envelope-from ) id 1hfqD3-0001SI-7V for qemu-devel@archiver.kernel.org; Tue, 25 Jun 2019 14:30:25 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:50722) by lists.gnu.org with esmtp (Exim 4.86_2) (envelope-from ) id 1hfqBA-0000XF-Uh for qemu-devel@nongnu.org; Tue, 25 Jun 2019 14:28:30 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hfqB8-0001Jw-Sk for qemu-devel@nongnu.org; Tue, 25 Jun 2019 14:28:28 -0400 Received: from mx1.redhat.com ([209.132.183.28]:43354) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1hfqB6-0001Cf-Tz for qemu-devel@nongnu.org; Tue, 25 Jun 2019 14:28:26 -0400 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 90740B0CF5 for ; Tue, 25 Jun 2019 18:28:05 +0000 (UTC) Received: from redhat.com (ovpn-112-73.ams2.redhat.com [10.36.112.73]) by smtp.corp.redhat.com (Postfix) with ESMTPS id D69515C22F; Tue, 25 Jun 2019 18:27:57 +0000 (UTC) Date: Tue, 25 Jun 2019 19:27:55 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Eric Blake Message-ID: <20190625182755.GN3139@redhat.com> References: <20190625161629.302-1-imammedo@redhat.com> <2647871f-34f2-0f8d-adb7-0265f951acd3@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <2647871f-34f2-0f8d-adb7-0265f951acd3@redhat.com> User-Agent: Mutt/1.11.4 (2019-03-13) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.26]); Tue, 25 Jun 2019 18:28:08 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 209.132.183.28 Subject: Re: [Qemu-devel] [libvirt] [PATCH v2] deprecate -mem-path fallback to anonymous RAM X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Cc: libvir-list@redhat.com, Igor Mammedov , qemu-devel@nongnu.org, dgilbert@redhat.com, ehabkost@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Tue, Jun 25, 2019 at 01:18:01PM -0500, Eric Blake wrote: > On 6/25/19 11:16 AM, Igor Mammedov wrote: > > Fallback might affect guest or worse whole host performance > > or functionality if backing file were used to share guest RAM > > with another process. > > > > Patch deprecates fallback so that we could remove it in future > > and ensure that QEMU will provide expected behavior and fail if > > it can't use user provided backing file. > > > > Signed-off-by: Igor Mammedov > > --- > > v2: > > * improve text language > > (Markus Armbruster ) > > > > Is this deprecation introspectible? Does it need to be? > > Do we even need a deprecation period, or can we declare this a bug fix > (it was a bug that we didn't fail outright on an impossible request) and > do it immediately? I think it is hard to call it a bug when we added explicit extra code to make it work as it does today. It is really a misguided feature. > If it is not a bug fix, perhaps it could be made introspectible by > having a new boolean parameter to opt in to the failure now, rather than > 2 releases from now? >From libvirt's POV I don't see a need for introspection. There's no special action we need to take to deal with the new behaviour - it is ultimately just providing the behaviour we kind of assumed it already had. Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|